1. Field of the Invention
The present invention relates in general to muffler systems of an automotive engines, and more particularly to the muffler systems of a controllable type that can control its sound muffling or dampening performance in accordance with engine speed or the like.
2. Description of Related Art
In order to clarify the task of the present invention, some known controllable muffler systems of the above-mentioned type will be briefly described with reference to the accompanying drawings.
In FIG. 8, there is shown one muffler system that is described in Japanese Patent First Provisional Publication 4-72408. The system of this publication generally comprises a chamber body 100A, an inlet pipe (no numeral) led into the chamber body 100A and two outlet pipes 101 and 102 extending to the outside from the interior of the chamber body 100A. The outlet pipe 101 is equipped with a control valve 103 that is controlled in accordance with an operation condition (e.g. engine speed) of an associated engine.
In FIG. 9, there is shown another known muffler system that is described in Japanese Utility Model First Provisional Publication 4-54917. The system of this publication generally comprises a chamber body 100B and two inlet pipes 104 and 105 of which upstream ends are mated. The inlet pipe 104 passes through the chamber body 100B, having small openings thereof exposed to the interior of the chamber body 100B, while the other inlet pipe 105 is led into a middle position of the chamber body 100B. The inlet pipe 104 is equipped with a control valve 106 that is controlled in accordance with an operation condition (e.g. engine speed) of an associated engine.
Due to provision of the control valves 103 and 106, the above-mentioned known muffler systems can exhibit optimum performance in accordance with the engine operation condition. However, increase in cost can not be avoided because of employment of the control valves 103 and 106 which are actuated by complicated electronic control systems.
In FIG. 10, there is shown still another known muffler system that is described in Japanese Patent First Provisional Publication 10-131738, which can be produced at relatively low cost. The system generally comprises a chamber body 100C, an inlet pipe, an outlet pipe and an inner pipe 107. The inner pipe 107 is equipped at its downstream end with an exhaust pressure sensible valve 108. That is, the valve 108 is controlled to open/close the inner pipe 107 in accordance with a pressure difference created in the chamber body 100C.
However, even the system of FIG. 10 tends to fail to exhibit at 20 a satisfied performance because of the nature of the exhaust pressure sensible valve 108. In particular, adjustment of the valve 108 for obtaining a desired muffling performance is difficult.
Accordingly, an object of the present invention is to provide a controllable muffler system which is free of the above-mentioned drawbacks.
According to the present invention, there is provided a controllable muffler system which can be arranged entirely below a vehicle floor to obtain an optimum controllable muffling performance thereof.
According to a first aspect of the present invention, there is provided a controllable muffler system for use with an engine that produces a power by burning fuel, which comprises a first passage section extending from the engine for having an exhaust gas of the engine flow therethrough, the first passage section having a catalytic converter mounted thereon; a dual passage section including second and third passage sections which extend separately from an end of the first passage section, the second passage having a control valve for controlling the flow rate of the exhaust gas flowing therethrough; a fourth passage section extending from respective ends of the second and third passage sections to the open air, the fourth passage section having a rear muffler mounted thereon; and a control unit which controls the control valve of the second passage section in accordance with an operation condition of the engine.
According to a second aspect of the present invention, there is provided a controllable muffler system for use with an internal combustion engine, which comprises a first passage section extending from the engine for having an exhaust gas of the engine flow therethrough, the first passage section having a catalytic converter and a front muffler mounted thereon; a dual passage section including second and third passage sections which extend separately from an end of the first passage section, the second passage having a control valve for controlling the flow rate of the exhaust gas flowing therethrough; a fourth passage section extending from respective ends of the second and third passage sections to the open air, the fourth passage section having a rear muffler mounted thereon; and a control unit which controls the control valve of the second passage section in accordance with an operation condition of the engine.